Many advertisers are uncertain of the value of computer-based click advertising, but are more certain of the value of a telephone call from a prospective customer. The recognition of call value has given rise to various advertising programs that focus on delivering telephone calls to advertisers. Industry analysts have estimated that in 2013 more than $60 Billion was spent on advertising in the United States to persuade consumers to call a business. As opposed to click advertising, where the payout per click can be measured in cents or fraction of a cent, call based advertising pays orders of magnitudes more for quality calls. Unfortunately, such financial rewards have given rise to new forms of call spam and fraud.
Traditionally, spam blocking has been dependent on the people committing fraud retaining the same caller ID across multiple calls. That means that once a pattern has been identified either by a person or machine, the identified caller ID could be placed on a blacklist to prevent future calls. There are for example many sites on the Internet that list suspicious calls by caller ID. However, it has become increasingly easy for parties seeking to commit fraud to buy and use temporary phone numbers or to simply fake caller ID before making a call in order to circumvent fraud-prevention technologies based on caller ID.
There is therefore the need for a better method of spam and fraud detection that is not dependent on caller ID.